Compositions and methods for microbial enhanced digestion of polymers in fracking wells

ABSTRACT

The present invention provides environmentally-friendly compositions and methods for degrading polymers used in fracking operations to enhance the recovery of oil and gas. Specifically, the compositions and methods utilized microorganisms and/or their growth by-products to degrade polymers, such as PGA, PLA and PAM, used in fracking wells.

CROSS-REFERENCE TO A RELATED APPLICATION

This application is a continuation of co-pending U.S. patent applicationSer. No. 16/490,185, filed Aug. 30, 2019; which is a National StageApplication of International Application No. PCT/US2018/020706, filedMar. 2, 2018; which claims the benefit of the following U.S. provisionalapplications: Ser. No. 62/466,410, filed Mar. 3, 2017; and Ser. No.62/528,718, filed Jul. 5, 2017; each of which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

Hydraulic fracturing, or “fracking,” of earth formations around awellbore is a process used to increase a well's productivity. Standardvertical wells undergo fracturing during original production or tostimulate production. Other applications involve the use of horizontalwells, wherein a vertical well is drilled to a desired depth, at whichpoint the drill is turned to begin drilling horizontally. The horizontalportion of these wells can extend several thousands of feet in length.

Once drilling has occurred, thousands of gallons of “pad” fluid, anoil-based or water-based fluid, are injected into a formation at extremepressures. This causes cracks or fractures to develop in the face of therock at the wellbore. Continued fluid injection into the well thencauses the fractures to increase in length and width. After a sufficientwidth is achieved, particles called “proppant” are added to the fluid,often coated with polymer materials to aid in proper functioning intight subterranean formations. Silica sand is commonly used as aproppant in fracking applications.

After fluid injection has ceased, fracturing fluid flows out of thefractures, allowing the walls of the fractures to close on the proppant.The proppant particles then “prop” the walls of the fractures apart.Because proppant particles are normally much larger than the particlesof the formation, the fluid permeability of a propped fracture is muchgreater than that of the natural formation; hence, the flow capacity ofthe well is increased. At the end of a fracturing treatment,proppant-laden fluid is “flushed” from the wellbore into the formationby a proppant-free displacement fluid.

Despite the increases in oil and gas productivity associated with theuse of fracking, certain drawbacks and complications can arise,particularly with regard to the use of proppants. For example, dependingon the proppant used, the proppant can affect flow rate of thefracturing fluid, and/or the proppant can be deposited improperly, ornot deposited at all, into fractures. As a result, a variety ofsolutions for overcoming these complications have been developed, suchas proppant coatings and chemical fracturing fluid additives.

Theoretical models generally indicate that the width of a fracture atthe wellbore increases with effective viscosity of the injected fluid inthe fracture, rate of fluid injection and volume of fluid injected. Thefracturing fluid must be able to support the high pressures necessaryfor creating fractures with a width that can accept proppant. Ideally,this is done without using large quantities of fluid; however, theviscosity of a fracturing fluid is normally limited by pressure loss asthe fluid is pumped down a wellbore. Fracturing fluids that arecurrently used minimize this pressure loss by employing polymersolutions that are highly non-Newtonian (shear-thinning). Otherwise,pressure loss due to friction in the tubing would only allow injectionat very small rates. Water-soluble polymers can be cross-linked toincrease viscosity, and this cross-linking is sometimes delayed todecrease pressure loss in tubulars.

Friction reducers can also be added to fracking fluids to lower frictionpressure during pumping. Friction reducers are typically long chain,high molecular weight water soluble polymers. They operate by increasinglaminar flow and decreasing turbulent flow in water as it is pumped downthe wellbore, thus decreasing the energy required to move water andproppant particles down the well.

Furthermore, breakers can be used to lower the fracturing fluid'sviscosity before the fluid flows back up the well. After the proppant ismixed or coated with the viscous fracturing fluid and pumped downhole toform a fracture, the fracturing fluid must be removed from the proppantpack. Unbroken fracturing fluid left in the fracture can reduce proppantpack permeability, resulting in less fluid flowback and less oil and gasproduction. Ideally, fracturing fluid is removed without moving theproppant from the fracture and without damaging the conductivity of theproppant bed. To accomplish this, the viscous fluid that carried theproppant can be thinned to a near-water state using breakers, such asenzymes or oxidizers.

Flowback of proppant from fractures and into the wellbore can alsohinder the efficiency of oil and gas production. If proppant flows outof a fracture into the well, the fracture width decreases andhydrocarbon productivity declines. Polymeric fibers made of, forexample, polylactide, or polylactic acid (PLA), have been used toprevent proppant flowback. The PLA fibers help suspend the proppant inthe fracturing fluid and carry it down the well bore and into theformation. The fibers act to form a network that stabilizes the proppantpack, which is then deposited in the fractures, while preventingproppant settling at the bottom of the fracture. The polylactide fibersthen dissolve, leaving “wormholes” through which gas and oil can flowinto the well. PLA can also be used in the form of dissolvable ballsand/or flakes as a friction reducer.

Another commonly used biodegradable polymer in fracking operations ispolyglycolide, or polyglycolic acid (PGA), in the form of balls orfibers. Variable sized fracking balls are often used for the fracking ofmultiple frac zones. Use of balls allows untreated zones to be isolatedfrom already treated zones so that hydraulic pressure fractures the newzones instead of merely disrupting the already-fracked zones. Theprocess involves inserting a plurality of frac sleeves, which include amechanically-actuated sliding sleeve engaged by a ball seat, into anuntreated zone. The frac sleeves may have progressively smaller ballseats.

The smallest frac balls are inserted into the sleeves first, passingthrough all but the last and smallest frac sleeve, where they seat.Applied pressure from the surface causes the frac ball to press againstthe ball seat, which mechanically engages a sliding sleeve. The pressurecauses the sleeve to mechanically shift, opening a plurality of fracports and exposing the formation. High-pressure fracking fluid isinjected from the surface, forcing the frac fluid into the formation,and the zone is fracked. After the zone is fracked, the second-smallestfrac ball is pumped into the well bore, and seats in the furthestavailable sleeve. That zone is fracked, and the process is continuedwith increasingly larger frac balls, the largest ball being insertedlast.

Additionally, many well operators use polyacrylamide (PAM) gel as afriction reducer in amounts around 1 to 2 parts per 1,000 gallons ofwater; however, once the gel is downwell it serves no other purpose,does not degrade readily, and is not easily recovered back to thesurface. Ineffective attempts to cleave the gel using sodium chromite orsodium bromide have been made, but often leave significant amounts ofremaining gel.

The utility of polymeric fracking substances is limited by theircapacity to degrade under temperature and moisture conditions that existin a well, as well as their ability to be recovered back up the well.Increasing the viscosity of fracturing fluids creates even furtherlimitations, as the water-soluble polymers most commonly used toincrease the viscosity do not completely degrade. Instead, they leave aresidue that hinders the flow capacity of the proppant left in thefracture. Additionally, polymers used as friction reducers, breakers,crosslinkers, or other additives can lead to similar difficulties due totheir slow rate of degradation.

The rate at which PLA or PGA degrades, for example, is important forsuccessful application in subterranean settings, such as those describedabove. The degradation of PIA and PGA is thought to proceed mainlythrough hydrolysis, and the degradation rate is highly dependent onlocal conditions, e.g., temperature. These cross-linked polymers aresubjected to very high temperatures in the formations, which decreaserapidly as fluid is pumped through well tubing.

Thus, there is a need for compositions and methods for quickly degradingand recovering PLA, PGA and other polymeric substances used as frictionreducers, breakers, and/or other fracturing fluid additives andcoatings.

BRIEF SUMMARY OF THE INVENTION

The subject invention provides microbes, as well as by-products of theirgrowth, such as biosurfactants, solvents and/or enzymes. The subjectinvention also provides methods of using these microbes and theirby-products in hydraulic fracking operations to enhance the dissolutionof polymeric fracturing fluid additives and/or proppant coatings.Advantageously, the methods of the subject invention areenvironmentally-friendly, operational-friendly and cost-effective.

In preferred embodiments, the subject invention provides materials andmethods for improving oil and gas production by treating an oil and gascontaining formation undergoing hydraulic fracturing treatment with amicrobe-based composition capable of dissolving polymers that have beenapplied as, for example, fracturing fluid additives and/or proppantcoatings.

In one embodiment, the subject invention provides a microbe-basedcomposition for enhancing oil and gas recovery from ahydrocarbon-bearing formation, the composition comprising amicroorganism and/or its growth by-products. The growth by-products canbe, for example, biosurfactants, solvents, enzymes and/or othermetabolites.

In one embodiment, the microbe is one or more biosurfactant-, solvent-and/or enzyme-producing bacteria or yeasts, or a combination thereof. Inone embodiment, the microbe-based composition comprises a “killeryeast,” such as, for example, Wickerhamomyces anomalus, and/or productsof the growth of this species. In one embodiment, the microbe is aStarmerella clade yeast. In one embodiment the microbe is a Bacillusclade bacteria.

In one embodiment, the microbe-based composition can further compriseenzymes that enhance degradation of polymers, such as, for example,proteases, lipases and/or esterases.

In one embodiment, the microbe-based composition can further comprisematerials to enhance microbe growth during application. These materialscan be, for example, nutrients and/or germination enhancers. Thenutrient sources can include, for example, nitrogen, nitrates, nitrites,phosphorus, magnesium and/or carbon. The germination enhancers caninclude, for example, L-alanine, L-valine, L-asparagine and/or manganesein micromolar amounts.

In certain embodiments, the compositions of the subject invention haveadvantages over, for example, biosurfactants, solvents, and/or enzymesalone, including one or more of the following: high concentrations ofmannoprotein as a part of a yeast cell wall's outer surface; thepresence of beta-glucan in yeast cell walls; and the presence ofbiosurfactants and other metabolites (e.g., lactic acid, ethanol, ethylacetate, etc.) in the culture. These metabolites can, for example, actas solvents.

In one embodiment, the subject invention provides yeast fermentationproducts that can be used to digest, or enhance the degradation of,polymers in fracking wells. The yeast fermentation product can beobtained via cultivation of a biosurfactant-, solvent- and/orenzyme-producing yeast, such as, for example, Wickerhamomyces anomalus(Pichia anomala). The fermentation broth after 7 days of cultivation at25-30° C. can contain the yeast cell suspension and, for example, 4 g/Lor more of biosurfactant.

The yeast fermentation product can also be obtained via cultivation of abiosurfactant-, solvent- and/or enzyme-producing yeast, such as, forexample, Starmerella bombicola. The fermentation broth after 5 days ofcultivation at 25° C. can contain the yeast cell suspension and, forexample, 100 g/L or more of biosurfactant.

In one embodiment, the composition according to the subject invention isobtained through cultivation processes ranging from small to largescale. The cultivation process can be, for example, submergedcultivation, solid state fermentation (SSF), and/or a combinationthereof.

As shown in FIGS. 1 and 2, the yeast fermentation products can beincubated with fracking fluid containing, for example, PLA balls, for 24hours. A PLA ball after incubation with the yeast fermentation productwas completely dissolved, whereas when incubated for the same timeperiod with water alone, only 1% total dissolution occurred (requiringapproximately one month to dissolve completely).

Advantageously, the subject microbe-based compositions can be used todigest, or enhance the degradation of, polymers in, for example,fracking wells. The subject composition can also be useful as a flowbacksolution, wherein the biosurfactants and other microbial growthby-products can efficiently decrease water surface tension to adesirable range of, for example, 28-30 dynes/cm. The compositions canalso help reduce the energy input required for flushing out frackingmaterials post-use.

In one embodiment the subject invention provides a method for improvingoil and gas production efficiency by applying a composition comprising abiosurfactant-, solvent- and/or enzyme-producing microorganism, and/or agrowth by-product thereof, to an oil well. The growth by-product can beany microbial metabolite, such as, for example, a biosurfactant, asolvent and/or an enzyme.

In one embodiment the method can be used for enhancing oil and gasrecovery by applying the microbe-based composition to an oil wellundergoing hydraulic fracking treatment.

The method can further comprise adding materials to enhance microbegrowth and/or germination during application (e.g., adding nutrients topromote microbial growth and/or germination enhancers). In oneembodiment, the nutrient sources can include, for example, nitrogen,nitrate, phosphorus, magnesium and/or carbon. In one embodiment, thegermination enhancers can include, for example, L-alanine, L-valine,L-asparagine and/or manganese in micromolar amounts.

In one embodiment, the method can further comprise addingpolymer-degrading enzymes to the site in order to enhance polymerdegradation.

Preferably, the microbes of the microbe-based composition and/or theirgrowth byproducts can quickly digest polymers such as polylactic acid(PLA) and/or polyglycolic acid (PGA). The microbes can be inactive, live(or viable), or in spore form, at the time of application.

In one embodiment, the microorganism is a yeast, for example,Wickerhamomyces anomalus and/or Starmerella bombicola. In oneembodiment, the microorganism is a bacteria, such as, for example, aspecies of Bacillus clade bacteria. In one embodiment, a combination ofmicroorganisms is utilized in the microbe-based composition.

The microorganisms can grow in situ and produce active compounds onsite.Consequently, a high concentration of, for example, biosurfactant,solvent, and/or enzyme, and biosurfactant-producing microorganisms at atreatment site (e.g., an oil well) can be achieved easily andcontinuously.

In one embodiment, the subject invention provides methods of recoveringpolymeric substances that remain in fracking wells. For example,biosurfactants produced by methods and microorganisms of the presentinvention can reduce interfacial tension of fluids used for upliftingpolymeric fracking substances, such as polyacrylamide (PAM) gel frictionreducers. In another embodiment, the biosurfactants can be used tocleave PAM gel prior to uplifting.

The subject invention can be useful for well completion, particularly infracking operations, as well as restoring the health of oil andgas-bearing formations. For example, the subject compositions andmethods can aid in the repair of formation damage in the areassurrounding a wellbore, and can remediate polymers (e.g., PLA and PGA)and biopolymers (e.g., guar gum and xanthan gum) that are leftover fromprevious fracking operations. Thus, clogged channels can be opened upwithin formations to allow for further fracking opportunities.

In one embodiment, the subject invention provides methods of producing abiosurfactant, solvent, metabolite, and/or an enzyme by cultivating amicrobe strain of the subject invention under conditions appropriate forgrowth and surfactant, solvent, metabolite, and/or enzyme production;and purifying the surfactant, solvent, metabolite, and/or enzyme forsubsequent use according to the subject invention.

Advantageously, the present invention can be used without releasinglarge quantities of inorganic compounds into the environment.Additionally, the compositions and methods utilize components that arebiodegradable and toxicologically safe. Thus, the present invention canbe used in all possible operations of oil and gas production as a“green” treatment.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows a PLA ball (left) and a dissolved PLA ball afterapplication of yeast treatment (right).

FIG. 2 shows PLA digestion over a 24 hour period using yeast digestiontreatment (middle) versus water alone (right). Yeast digestion resultedin complete dissolution, whereas water alone only resulted in about 1%dissolution.

DETAILED DESCRIPTION OF THE INVENTION

The subject invention provides microbes, as well as by-products of theirgrowth, such as biosurfactants, solvents and/or enzymes. The subjectinvention also provides methods of using these microbes and theirby-products in hydraulic fracking operations to enhance the dissolutionof polymeric fracturing fluid additives and/or proppant coatings.Advantageously, the methods of the subject invention areenvironmentally-friendly, operational-friendly and cost-effective.

In preferred embodiments, the subject invention provides materials andmethods for improving oil and gas production by treating an oil and gascontaining formation undergoing hydraulic fracturing treatment with amicrobe-based composition capable of dissolving polymers that have beenapplied as, for example, fracturing fluid additives and/or proppantcoatings.

In one embodiment, the subject invention provides a microbe-basedcomposition for enhancing oil and gas recovery from ahydrocarbon-bearing formation, the composition comprising amicroorganism and/or its growth by-products. The growth by-products canbe, for example, biosurfactants, solvents, enzymes and/or othermetabolites.

In one embodiment the subject invention provides a method for improvingoil and gas production efficiency by applying a composition comprising abiosurfactant-, solvent- and/or enzyme-producing microorganism, and/or agrowth by-product thereof, to an oil well. The growth by-product can beany microbial metabolite, such as, for example, a biosurfactant, asolvent and/or an enzyme.

Selected Definitions

As used herein, reference to a “microbe-based composition” means acomposition that comprises components that were produced as the resultof the growth of microorganisms or other cell cultures. Thus, themicrobe-based composition may comprise the microbes themselves and/orby-products of microbial growth. The microbes may be in a vegetativestate, in spore form, in mycelial form, in any other form of propagule,or a mixture of these. The microbes may be planktonic or in a biofilmform, or a mixture of both. The by-products of growth may be, forexample, metabolites, cell membrane components, expressed proteins,and/or other cellular components. The microbes may be intact or lysed.In preferred embodiments, the microbes are present, with broth in whichthey were grown, in the microbe-based composition. The cells may bepresent at, for example, a concentration of 1×10⁴, 1×10⁵, 1×10⁶, 1×10⁷,1×10⁸, 1×10⁹, 1×10¹⁰, or 1×10¹¹ or more propagules per milliliter of thecomposition. As used herein, a propagule is any portion of amicroorganism from which a new and/or mature organism can develop,including but not limited to, cells, spores, conidia, mycelia, buds andseeds.

The subject invention further provides “microbe-based products,” whichare products that are to be applied in practice to achieve a desiredresult. The microbe-based product can be simply the microbe-basedcomposition harvested from the microbe cultivation process.Alternatively, the microbe-based product may comprise furtheringredients that have been added. These additional ingredients caninclude, for example, stabilizers, buffers, appropriate carriers, suchas water, salt solutions, or any other appropriate carrier, addednutrients to support further microbial growth, non-nutrient growthenhancers, such as plant hormones, and/or agents that facilitatetracking of the microbes and/or the composition in the environment towhich it is applied. The microbe-based product may also comprisemixtures of microbe-based compositions. The microbe-based product mayalso comprise one or more components of a microbe-based composition thathave been processed in some way such as, but not limited to, filtering,centrifugation, lysing, drying, purification and the like.

As used herein, an “isolated” or “purified” nucleic acid molecule,polynucleotide, polypeptide, protein or organic compound such as a smallmolecule (e.g., those described below), is substantially free of othercompounds, such as cellular material, with which it is associated innature. As used herein, reference to “isolated” in the context of amicrobial strain means that the strain is removed from the environmentin which it exists in nature. Thus, the isolated strain may exist as,for example, a biologically pure culture, or as spores (or other formsof the strain) in association with a carrier.

In certain embodiments, purified compounds are at least 60% by weight(dry weight) the compound of interest. Preferably, the preparation is atleast 75%, more preferably at least 90%, and most preferably at least99%, by weight the compound of interest. For example, a purifiedcompound is one that is at least 90%, 91%, 92%, 93%, 94%, 95%, 98%, 99%,or 100% (w/w) of the desired compound by weight. Purity is measured byany appropriate standard method, for example, by column chromatography,thin layer chromatography, or high-performance liquid chromatography(HPLC) analysis. A purified or isolated polynucleotide (ribonucleic acid(RNA) or deoxyribonucleic acid (DNA)) is free of the genes or sequencesthat flank it in its naturally-occurring state. A purified or isolatedpolypeptide is free of the amino acids or sequences that flank it in itsnaturally-occurring state.

As used herein, “applying” a composition or product refers to contactingit with a target or site such that the composition or product can havean effect on that target or site. The effect can be due to, for example,microbial growth and/or the action of a biosurfactant or other growthby-product. For example, the microbe-based compositions or products canbe injected into oil wells and/or the piping, pumps, tanks, etc.associated with oil wells.

As used herein, a “biofilm” is a complex aggregate of microorganisms,such as bacteria, wherein the cells adhere to each other. The cells inbiofilms are physiologically distinct from planktonic cells of the sameorganism, which are single cells that can float or swim in liquidmedium.

As used herein, “harvested” in the context of fermentation ofmicroorganisms refers to removing some or all of the microbe-basedcomposition from a growth vessel.

A “metabolite” refers to any substance produced by metabolism or asubstance necessary for taking part in a particular metabolic process. Ametabolite can be an organic compound that is a starting material (e.g.,glucose), an intermediate (e.g., acetyl-CoA), or an end product (e.g.,n-butanol) of metabolism. Examples of metabolites can include, but arenot limited to, enzymes, toxins, acids, solvents, alcohols, proteins,carbohydrates, vitamins, minerals, microelements, amino acids, polymers,and biosurfactants.

As used herein, “modulate” is interchangeable with alter (e.g., increaseor decrease). Such alterations are detected by standard art knownmethods such as those described herein.

As used herein, “surfactant” refers to a compound that lowers thesurface tension (or interfacial tension) between two liquids or betweena liquid and a solid. Surfactants act as detergents, wetting agents,emulsifiers, foaming agents, and/or dispersants. A surfactant producedby microorganisms is referred to as a “biosurfactant.”

In some embodiments, the microbes used according to the subjectinvention are “surfactant over-producing.” For example, the strain mayproduce at least 0.1-10 g/L, e.g., 0.5-1 g/L surfactant. For example,the strain may produce at least 10%, 25%, 50%, 100%, 2-fold, 5-fold, 7.5fold, 10-fold, 12-fold, 15-fold or more surfactant compared to otheroil-recovery microbial strains. In one embodiment, where Bacillussubtilis is used according to the subject invention, Bacillus subtilisATCC 39307 is used herein as a reference strain.

Ranges provided herein are understood to be shorthand for all of thevalues within the range. For example, a range of 1 to 20 is understoodto include any number, combination of numbers, or sub-range from thegroup consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,16, 17, 18, 19 or 20 as well as all intervening decimal values betweenthe aforementioned integers such as, for example, 1.1, 1.2, 1.3, 1.4,1.5, 1.6, 1.7, 1.8, and 1.9. With respect to sub-ranges, “nestedsub-ranges” that extend from either end point of the range arespecifically contemplated. For example, a nested sub-range of anexemplary range of 1 to 50 may comprise 1 to 10, 1 to 20, 1 to 30, and 1to 40 in one direction, or 50 to 40, 50 to 30, 50 to 20, and 50 to 10 inthe other direction.

As used herein, “reduces” refers to a negative alteration of at least1%, 5%, 10%, 25%, 50%, 75%, or 100%.

As used herein, “reference” refers to a standard or control condition.

As used herein, “oil and natural gas production” refers to any and alloperations involved in the extraction of crude oil and/or natural gasfrom the earth, processing, and through its eventual purchase and use byconsumers. Oil and natural gas production can include, but is notlimited to, drilling, pumping, recovering, fracking, water-flooding,transmission, processing, refining, transportation, and storage of oiland/or gas.

As used herein, “enhancing oil and gas recovery” means increasing orimproving the quality and/or quantity of oil and/or gas extracted andultimately produced from an oil and gas containing site.

As used herein, “polymer” refers to any macromolecular compound preparedby bonding one or more similar molecular units, or monomers, together.Polymers include synthetic and natural polymers. Exemplary polymersinclude rubbers, starches, resins, guar gum, neoprene, nylon, PVC,silicone, cellulose, polystyrene, polyethylene, polypropylene,polyacrylonitrile, polyamines, polysaccharides, polynucleotides,polybutylene adipate terephthalate (PBAT), polyhydroxyalkanoates (PHAs),polybytlene succinate (PBS), polycaprolactone (PCL), polyglycolic acid(PGA), polyhydroxybutyrates (PHBs), polyesters such as polylactide(PLA), polyacrylamides (PAM), and others.

As used herein, “degradation” of a polymer can be used interchangeablywith “dissolution,” “digestion,” and “remediation” and refers to thebreakdown or depolymerization of the polymer into more water soluble,lower molecular weight molecules capable of flowing out of a wellborefracture. Degradation can occur by any means, including but not limitedto photo-induced degradation, thermal degradation, chemical degradation,such as ozonolysis, hydrolysis, or oxidation, and biodegradation.

As used herein, “polymer-degrading enzyme” refers to any enzyme capableof degrading or enhancing the degradation or dissolution of a polymer.Non-limiting examples of polymer-degrading enzymes include proteases (orproteinases, or proteinase enzymes), esterases, and lipases. Proteaseenzymes have been shown to hasten the hydrolysis or degradation of PLA.Esterases and lipases may also be suitable for other degradablepolymers, such as poly(hydroxybutyrates) or aliphatic polyesters.Typically, these enzymes are isolated from plants, animals, bacteria,and fungi, and can also be obtained commercially.

The transitional term “comprising,” which is synonymous with“including,” or “containing,” is inclusive or open-ended and does notexclude additional, unrecited elements or method steps. By contrast, thetransitional phrase “consisting of” excludes any element, step, oringredient not specified in the claim. The transitional phrase“consisting essentially of” limits the scope of a claim to the specifiedmaterials or steps “and those that do not materially affect the basicand novel characteristic(s)” of the claimed invention.

Unless specifically stated or obvious from context, as used herein, theterm “or” is understood to be inclusive. Unless specifically stated orobvious from context, as used herein, the terms “a”, “an”, and “the” areunderstood to be singular or plural.

Unless specifically stated or obvious from context, as used herein, theterm “about” is understood as within a range of normal tolerance in theart, for example, within 2 standard deviations of the mean. “About” canbe understood as within 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.5%,0.1%, 0.05%, or 0.01% of the stated value. Unless otherwise clear fromcontext, all numerical values provided herein are modified by the termabout.

The recitation of a listing of chemical groups in any definition of avariable herein includes definitions of that variable as any singlegroup or combination of listed groups. The recitation of an embodimentfor a variable or aspect herein includes that embodiment as any singleembodiment or in combination with any other embodiments or portionsthereof.

Any compositions or methods provided herein can be combined with one ormore of any of the other compositions and methods provided herein.

Other features and advantages of the invention will be apparent from thefollowing description of the preferred embodiments thereof, and from theclaims. All references cited herein are hereby incorporated byreference.

Microbial Strains Grown in Accordance with the Subject Invention

The microorganisms grown according to the systems and methods of thesubject invention can be, for example, bacteria, yeast and/or fungi.These microorganisms may be natural, or genetically modifiedmicroorganisms. For example, the microorganisms may be transformed withspecific genes to exhibit specific characteristics. The microorganismsmay also be mutants of a desired strain. As used herein, “mutant” meansa strain, genetic variant or subtype of a reference microorganism,wherein the mutant has one or more genetic variations (e.g., a pointmutation, missense mutation, nonsense mutation, deletion, duplication,frameshift mutation or repeat expansion) as compared to the referencemicroorganism. Procedures for making mutants are well known in themicrobiological art. For example, UV mutagenesis and nitrosoguanidineare used extensively toward this end.

In one embodiment, the microorganism is a yeast or fungus. Yeast andfungus species suitable for use according to the current invention,include Candida, Saccharomyces (S. cerevisiae, S. boulardii sequela, S.torula), Issatchenkia, Kluyveromyces, Pichia, Wickerhamomyces (e.g., W.anomalus), Starmerella (e.g., S. bombicola), Mycorrhiza, Mortierella,Phycomyces, Blakeslea, Thraustochytrium, Phythium, Entomophthora,Aureobasidium pullulans, Pseudozyma aphidis, Fusarium venenalum,Aspergillus, Trichoderma (e.g., T. reesei, T. harzianum, T. hamatum, T.viride), and/or Rhizopus spp.

In one embodiment, the yeast is a killer yeast. As used herein, “killeryeast” means a strain of yeast characterized by its secretion of toxicproteins or glycoproteins, to which the strain itself is immune. Theexotoxins secreted by killer yeasts are capable of killing other strainsof yeast, fungi, or bacteria. For example, microorganisms that can becontrolled by killer yeast include Fusarium and other filamentous fungi.Examples of killer yeasts according to the present invention are thosethat can be used safely in the food and fermentation industries, e.g.,beer, wine, and bread making; those that can be used to control othermicroorganisms that might contaminate such production processes; thosethat can be used in biocontrol for food preservation; those than can beused for treatment of fungal infections in both humans and plants; andthose that can be used in recombinant DNA technology. Such yeasts caninclude, but are not limited to, Wickerhamomyces, Pichia (e.g., P.anomala, P. guielliermondii, P. kudriavzevii, P. occidentalis),Hansenula, Saccharomyces, Hanseniaspora, (e.g., H. uvarum), Ustilagomaydis, Debaryomyces hansenii, Candida, Cryptococcus, Kluyveromyces,Torulopsis, Ustilago, Williopsis, Zygosaccharomyces (e.g., Z. bailii)and others.

In certain embodiments, the microbial strain is a Pichia yeast selectedfrom Pichia anomala (Wickerhamomyces anomalus), Pichia guilliermondii,and Pichia kudriavzevii. Wickerhamomyces anomalus, in particular, is aneffective producer of various solvents, enzymes, killer toxins, as wellas sophorolipid biosurfactants.

In one embodiment, the microbial strain is chosen from the Starmerellaclade. A culture of a Starmerella microbe useful according to thesubject invention, Starmerella bombicola, can be obtained from theAmerican Type Culture Collection (ATCC), 10801 University Blvd.,Manassas, Va. 20110-2209 USA. The deposit has been assigned accessionnumber ATCC No. 22214 by the depository.

In one embodiment, the subject invention provides the use of yeaststrain ATCC 22214 and mutants thereof. This strain is an effectiveproducer of sophorolipid biosurfactants.

In preferred embodiments, the microorganisms are bacteria, includingGram-positive and Gram-negative bacteria. The bacteria may be, forexample Bacillus (e.g., B. subtilis, B. licheniformis, B. firmus, B.laterosporus, B. megaterium, B. amyloliquifaciens), Clostridium (C.butyricum, C. tyrobutyricum, C. acetobutyricum, Clostridium NIPER 7, andC. beijerinckii), Azobacter (A. vinelandil, A. chroococcum), Pseudomonas(P. chlororaphis subsp. aureofaciens (Kluyver), P. aeruginosa),Agrobacterium radiobacter, Azospirillumbrasiliensis, Rhizobium,Sphingomonas paucimobilis, Ralslonia eulropha, and/or Rhodospirillumrubrum.

In one embodiment, the microorganism is a strain of B. subtilis, suchas, for example, B. subtilis var. locuses B1 or B2, which are effectiveproducers of, for example, surfactin and other biosurfactants, as wellas biopolymers. This specification incorporates by referenceInternational Publication No. WO 2017/044953 A1 to the extent it isconsistent with the teachings disclosed herein. In another embodiment,the microorganism is a strain of Bacillus licheniformis, which is aneffective producer of biosurfactants as well as biopolymers, such aslevan.

In certain embodiments, the present invention utilizes Bacillus subtilisstrains with enhanced biosurfactant production compared to wild typeBacillus subtilis as well as compared to other microbes used in oilrecovery. Such Bacillus subtilis have been termed members of the Bseries, including, but not limited to, B1, B2 and B3.

In preferred embodiments, such strains are characterized by enhancedbiosurfactant production compared to wild type Bacillus subtilisstrains. In certain embodiments, the Bacillus subtilis strains haveincreased biopolymer solvent and/or enzyme production.

The B strain series of Bacillus subtilis produce more biosurfactantcompared to reference strains of Bacillus subtilis. Furthermore, theBacillus subtilis strains survive under high salt and anaerobicconditions better than other well-known Bacillus strains. The strainsare also capable of growing under anaerobic conditions. The Bacillussubtilis B series strains can also be used for producing enzymes thatdegrade or metabolize oil or other petroleum products.

In certain embodiments, the Bacillus subtilis strains are salt tolerant.Salt tolerance can be with respect to any one or more of a variety ofsalts. For example, the salt can be a monovalent salt such as a sodiumor potassium salt, e.g., NaCl or KCl, or a divalent salt such as amagnesium or calcium salt, e.g., MgCl₂ or CaCl₂, or a trivalent salt.

In some embodiments, the Bacillus subtilis strains are capable ofthriving under low oxygen conditions.

Other microbial strains including, for example, strains capable ofaccumulating significant amounts of, for example,glycolipid-biosurfactants, can be used in accordance with the subjectinvention. Other microbial by-products useful according to the presentinvention include mannoprotein, beta-glucan and other metabolites thathave bio-emulsifying and surface/interfacial tension-reducingproperties.

Growth of Microbes According to the Subject Invention

The subject invention utilizes methods for cultivation of microorganismsand production of microbial metabolites and/or other by-products ofmicrobial growth. The subject invention further utilizes cultivationprocesses that are suitable for cultivation of microorganisms andproduction of microbial metabolites on a desired scale. Thesecultivation processes include, but are not limited to, submergedfermentation, solid state fermentation (SSF), and combinations thereof.

The microbial cultivation systems would typically use submerged culturefermentation; however, surface culture and hybrid systems can also beused. As used herein “fermentation” refers to growth of cells undercontrolled conditions. The growth could be aerobic or anaerobic.

In one embodiment, the subject invention provides materials and methodsfor the production of biomass (e.g., viable cellular material),extracellular metabolites (e.g. small molecules and excreted proteins),residual nutrients and/or intracellular components (e.g. enzymes andother proteins).

The microbe growth vessel used according to the subject invention can beany fermenter or cultivation reactor for industrial use. In oneembodiment, the vessel may have functional controls/sensors or may beconnected to functional controls/sensors to measure important factors inthe cultivation process, such as pH, oxygen, pressure, temperature,agitator shaft power, humidity, viscosity and/or microbial densityand/or metabolite concentration.

In a further embodiment, the vessel may also be able to monitor thegrowth of microorganisms inside the vessel (e.g., measurement of cellnumber and growth phases). Alternatively, a daily sample may be takenfrom the vessel and subjected to enumeration by techniques known in theart, such as dilution plating technique. Dilution plating is a simpletechnique used to estimate the number of bacteria in a sample. Thetechnique can also provide an index by which different environments ortreatments can be compared.

In one embodiment, the method includes supplementing the cultivationwith a nitrogen source. The nitrogen source can be, for example,potassium nitrate, ammonium nitrate ammonium sulfate, ammoniumphosphate, ammonia, urea, and/or ammonium chloride. These nitrogensources may be used independently or in a combination of two or more.

The method of cultivation can provide oxygenation to the growingculture. One embodiment utilizes slow motion of air to remove low-oxygencontaining air and introduce oxygenated air. The oxygenated air may beambient air supplemented daily through mechanisms including impellersfor mechanical agitation of the liquid, and air spargers for supplyingbubbles of gas to the liquid for dissolution of oxygen into the liquid.

The method can further comprise supplementing the cultivation with acarbon source. The carbon source is typically a carbohydrate, such asglucose, sucrose, lactose, fructose, trehalose, mannose, mannitol,and/or maltose; organic acids such as acetic acid, fumaric acid, citricacid, propionic acid, malic acid, malonic acid, and/or pyruvic acid;alcohols such as ethanol, propanol, butanol, pentanol, hexanol,isobutanol, and/or glycerol; fats and oils such as soybean oil, canolaoil, rice bran oil, olive oil, corn oil, sesame oil, and/or linseed oil;etc. These carbon sources may be used independently or in a combinationof two or more.

In one embodiment, growth factors and trace nutrients for microorganismsare included in the medium. This is particularly preferred when growingmicrobes that are incapable of producing all of the vitamins theyrequire. Inorganic nutrients, including trace elements such as iron,zinc, copper, manganese, molybdenum and/or cobalt may also be includedin the medium. Furthermore, sources of vitamins, essential amino acids,and microelements can be included, for example, in the faun of flours ormeals, such as corn flour, or in the form of extracts, such as yeastextract, potato extract, beef extract, soybean extract, banana peelextract, and the like, or in purified forms. Amino acids such as, forexample, those useful for biosynthesis of proteins, can also beincluded, e.g., L-Alanine.

In one embodiment, inorganic salts may also be included. Usableinorganic salts can be potassium dihydrogen phosphate, dipotassiumhydrogen phosphate, disodium hydrogen phosphate, magnesium sulfate,magnesium chloride, iron sulfate, iron chloride, manganese sulfate,manganese chloride, zinc sulfate, lead chloride, copper sulfate, calciumchloride, calcium carbonate, and/or sodium carbonate. These inorganicsalts may be used independently or in a combination of two or more.

In some embodiments, the method for cultivation may further compriseadding additional acids and/or antimicrobials in the liquid mediumbefore, and/or during the cultivation process. Antimicrobial agents orantibiotics are used for protecting the culture against contamination.Additionally, antifoaming agents may also be added to prevent theformation and/or accumulation of foam when gas is produced duringcultivation.

The pH of the mixture should be suitable for the microorganism ofinterest. Buffers, and pH regulators, such as carbonates and phosphates,may be used to stabilize pH near a preferred value. When metal ions arepresent in high concentrations, use of a chelating agent in the liquidmedium may be necessary.

The method and equipment for cultivation of microorganisms andproduction of the microbial by-products can be performed in a batch, aquasi-continuous process, or a continuous process.

The microbes can be grown in planktonic form or as biofilm. In the caseof biofilm, the vessel may have within it a substrate upon which themicrobes can be grown in a biofilm state. The system may also have, forexample, the capacity to apply stimuli (such as shear stress) thatencourages and/or improves the biofilm growth characteristics.

In one embodiment, the method for cultivation of microorganisms iscarried out at about 5° to about 100° C., preferably, 15 to 60° C., morepreferably, 25 to 50° C. In a further embodiment, the cultivation may becarried out continuously at a constant temperature. In anotherembodiment, the cultivation may be subject to changing temperatures.

In one embodiment, the equipment used in the method and cultivationprocess is sterile. The cultivation equipment such as the reactor/vesselmay be separated from, but connected to, a sterilizing unit, e.g., anautoclave. The cultivation equipment may also have a sterilizing unitthat sterilizes in situ before starting the inoculation. Air can besterilized by methods know in the art. For example, the ambient air canpass through at least one filter before being introduced into thevessel. In other embodiments, the medium may be pasteurized or,optionally, no heat at all added, where the use of low water activityand low pH may be exploited to control bacterial growth.

The biomass content of the fermentation broth may be, for example, from5 g/l to 180 g/l or more. In one embodiment, the solids content of thebroth is from 10 g/l to 150 g/l.

The microbial growth by-product produced by microorganisms of interestmay be retained in the microorganisms or secreted into the growthmedium. In another embodiment, the method for producing microbial growthby-product may further comprise steps of concentrating and purifying themicrobial growth by-product of interest. In a further embodiment, thegrowth medium may contain compounds that stabilize the activity ofmicrobial growth by-product.

In one embodiment, metabolites are produced by cultivating a microbestrain of the subject invention under conditions appropriate for growthand metabolite production; and, optionally, purifying the metabolite.The metabolite can be any biosurfactant, enzyme, solvent, protein, acid,toxin, or other compound produced by the growth of the microbe.

In one embodiment, all of the microbial cultivation composition isremoved upon the completion of the cultivation (e.g., upon, for example,achieving a desired cell density, or density of a specified metabolitein the broth). In this batch procedure, an entirely new batch isinitiated upon harvesting of the first batch.

In another embodiment, only a portion of the fermentation product isremoved at any one time. In this embodiment, biomass with viable cellsremains in the vessel as an inoculant for a new cultivation batch. Thecomposition that is removed can be a cell-free broth or can containcells. In this manner, a quasi-continuous system is created.

Microbe-Based Compositions

In one embodiment, the subject invention provides a microbe-basedcomposition for enhancing oil and gas recovery from ahydrocarbon-bearing formation, the composition comprising amicroorganism and/or its growth by-products. The growth by-products canbe, for example, biosurfactants, solvents, enzymes and/or othermetabolites.

The subject composition can be used for degrading, or enhancing thedegradation of, polymeric additives in hydraulic fracking wells. Thecomposition can be used to efficiently digest polylactic acid (PLA) usedas a friction reducer, breaker, or other fracking fluid additive. Thecomposition can be used to digest, for example, PLA fibers, balls, orflakes. The composition can also be used to efficiently digestpolyglycolide (PGA), for example, in the form of fibers or frac balls.The composition can further be used to enhance oil and/or gas recovery.

Advantageously, the subject microbe-based compositions can be used todigest, or enhance the degradation of, polymers in, for example,fracking wells. The subject composition can also be useful as a flowbacksolution, wherein the biosurfactants and other microbial growthby-products can efficiently decrease water surface tension to adesirable range of, for example, 28-30 dynes/cm. The compositions canalso help reduce the energy input required for flushing out frackingmaterials post-use.

In preferred embodiments, the microbe-based composition comprisesmicroorganisms and/or their by-products. In one embodiment, the microbesused in the methods of the subject invention are one or morebiosurfactant-, solvent- and/or enzyme-producing bacteria or yeasts, ora combination thereof. In one embodiment, the microbe-based compositioncomprises a “killer yeast,” such as, for example, Wickerhamomycesanomalus, and/or products of the growth of this species. In oneembodiment, the microbe is a Starmerella clade yeast. In one embodimentthe microbe is a Bacillus clade bacteria.

The microbe-based composition can comprise the fermentation mediumcontaining a live culture and/or the microbial metabolites produced bythe microorganism and/or any residual nutrients. The product offermentation may be used directly without extraction or purification. Ifdesired, extraction and purification can be easily achieved usingstandard extraction and/or purification methods or techniques describedin the literature.

The microbe-based composition may comprise broth or medium in which themicrobes were grown. The product may be, for example, at least, byweight, 1%, 5%, 10%, 25%, 50%, 75%, or 100% broth. The amount of biomassin the product, by weight, may be, for example, anywhere from 0% to 100%inclusive of all percentages therebetween.

The biomass content of the fermentation broth may be, for example from 5g/l to 180 g/l or more. In one embodiment, the solids content of thebroth is from 10 g/l to 150 g/1.

Further components can be added to the microbe-based composition, forexample, buffering agents, carriers, other microbe-based compositionsproduced at the same or different facility, viscosity modifiers,preservatives, nutrients for microbe growth, tracking agents, biocide,other microbes, surfactants, emulsifying agents, lubricants, solubilitycontrolling agents, pH adjusting agents, preservatives, stabilizers andultra-violet light resistant agents.

In one embodiment, polymer-degrading enzymes can be included in themicrobe-based composition. The enzymes useful according to the presentinvention can include, for example, proteinases, esterases, lipases,oxidoreductases, hydrolases, lyases, cellulases, hemi-cellulases,pectinases, xanthanase, mannanase, α-galactosidase, amylase, andmixtures thereof, which are capable of degrading polymeric substrates atpH levels found in subterranean formations. In one embodiment, theenzyme is pronase. In another embodiment, the enzyme is proteinase K.

In certain embodiments, the enzymes may be spray-dried, freeze-dried, orthe like. In certain embodiments, the enzymes of the compositions may beprovided, inter alia, in a purified form, in a partially purified form,as whole cells, as whole cell lysates, or any combination thereof. Theconcentration of the enzymes should be an amount effective to hastenhydrolysis of the degradable polymer in the well bore to a desireddegree at given conditions. For instance, if a relatively fasterhydrolysis rate is desired, then a higher concentration of the chosenenzyme or mixture of enzymes could be included. The actual amountincluded will depend on, inter alia, the temperature of the well bore,the concentration of the degradable polymer, the particular enzymechosen, and the desired hydrolysis rate.

In one embodiment, the microbe-based composition can further comprisematerials to enhance microbe growth during application. These materialscan be, for example, nutrients and/or germination enhancers. Thenutrient sources can include, for example, nitrogen, nitrates, nitrites,phosphorus, magnesium and/or carbon, or any other nutrient source thatcan be used for cultivating the microbes as provided in this disclosure.The germination enhancers can include, for example, L-alanine, L-valine,L-asparagine and/or manganese in micromolar amounts.

In one embodiment, the composition can further comprise bufferingagents, including organic and amino acids or their salts, to stabilizepH near a preferred value. Suitable buffers include, but are not limitedto, citrate, gluconate, tartarate, malate, acetate, lactate, oxalate,aspartate, malonate, glucoheptonate, pyruvate, galactarate, glucarate,tartronate, glutamate, glycine, lysine, glutamine, methionine, cysteine,arginine and mixtures thereof. Phosphoric and phosphorous acids or theirsalts may also be used. Synthetic buffers are suitable to be used but itis preferable to use natural buffers such as organic and amino acids ortheir salts.

In a further embodiment, pH adjusting agents include potassiumhydroxide, ammonium hydroxide, potassium carbonate or bicarbonate,hydrochloric acid, nitric acid, sulfuric acid and mixtures thereof.

The pH of the microbe-based composition should be suitable for themicroorganism of interest. In a preferred embodiment, the pH of themicrobe-based composition ranges from 7.0-7.5.

In one embodiment, additional components such as an aqueous preparationof a salt, such as sodium bicarbonate or carbonate, sodium sulfate,sodium phosphate, or sodium biphosphate, can be included in themicrobe-based composition.

In certain embodiments, the compositions of the subject invention haveadvantages over, for example, biosurfactants or enzymes alone, includingone or more of the following: high concentrations of mannoprotein (abioemulsifier) as a part of yeast cell wall's outer surface; thepresence of biopolymer beta-glucan (an emulsifier) in yeast cell walls;the presence of biosurfactants in the culture that are capable ofreducing both surface and interfacial tension; and the presence ofsolvents and/or metabolites (e.g., lactic acid, ethanol, ethyl acetate,etc.).

Preparation of Microbe-Based Products

One microbe-based product of the subject invention is simply thefermentation broth containing the microorganism and/or the microbialmetabolites produced by the microorganism and/or any residual nutrients.The product of fermentation may be used directly without extraction orpurification. For example, the microbes and/or broth resulting from themicrobial growth can be removed from the growth vessel and transferredvia, for example, piping for immediate use.

If desired, extraction and purification can be easily achieved usingstandard extraction and/or purification methods or techniques describedin the literature.

Upon harvesting the microbe-based composition from the growth vessels,further components can be added as the harvested product is placed intocontainers and/or piped (or otherwise transported for use). Theadditives can be, for example, buffers, carriers, other microbe-basedcompositions produced at the same or different facility, viscositymodifiers, preservatives, nutrients for microbe growth, germinationenhancers, and the like.

In one embodiment, the composition (microbes, broth, or microbes andbroth) can be placed in containers of appropriate size, taking intoconsideration, for example, the intended use, the contemplated method ofapplication, the size of the fermentation tank, and any mode oftransportation from microbe growth facility to the location of use.Thus, the containers into which the microbe-based composition is placedmay be, for example, from 1 gallon to 1,000 gallons or more. In otherembodiments the containers are 2 gallons, 5 gallons, 25 gallons, orlarger.

Other microbial strains including, for example, other fungal strainscapable of digesting polymers such as PLA or accumulating significantamounts of, for example, glycolipid-biosurfactants and/or solventsand/or enzymes can be used in accordance with the subject invention.Biosurfactants and solvents that are useful according to the presentinvention include mannoprotein, beta-glucan, ethanol, lactic acid andother metabolites that have, for example, bio-emulsifying andsurface/interfacial tension-reducing properties. Enzymes usefulaccording to the present invention include polymer-degrading enzymesthat are capable of degrading polymeric substances in conditions (e.g.,pH and temperature) present in a subterranean formation.

Other suitable additives, which may be contained in the formulationsaccording to the invention, include substances that are customarily usedfor such preparations. Example of such additives include surfactants,emulsifying agents, lubricants, buffering agents, solubility controllingagents, pH adjusting agents, preservatives, stabilizers and ultra-violetlight resistant agents.

In one embodiment, the composition may further comprise buffering agentsincluding organic and amino acids or their salts. Suitable buffersinclude citrate, gluconate, tartarate, malate, acetate, lactate,oxalate, aspartate, malonate, glucoheptonate, pyruvate, galactarate,glucarate, tartronate, glutamate, glycine, lysine, glutamine,methionine, cysteine, arginine and a mixture thereof. Phosphoric andphosphorous acids or their salts may also be used. Synthetic buffers aresuitable to be used but it is preferable to use natural buffers such asorganic and amino acids or their salts listed above.

In a further embodiment, pH adjusting agents include potassiumhydroxide, ammonium hydroxide, potassium carbonate or bicarbonate,hydrochloric acid, nitric acid, sulfuric acid or a mixture.

In one embodiment, additional components such as an aqueous preparationof a salt as polyprotic acid such as sodium bicarbonate or carbonate,sodium sulfate, sodium phosphate, sodium biphosphate, can be included inthe formulation.

Advantageously, in accordance with the subject invention, themicrobe-based product may comprise broth in which the microbes weregrown. The product may be, for example, at least, by weight, 1%, 5%,10%, 25%, 50%, 75%, or 100% broth. The amount of biomass in the product,by weight, may be, for example, anywhere from 0% to 100% inclusive ofall percentages therebetween.

Optionally, the product can be stored prior to use. The storage time ispreferably short. Thus, the storage time may be less than 60 days, 45days, 30 days, 20 days, 15 days, 10 days, 7 days, 5 days, 3 days, 2days, 1 day, or 12 hours. In a preferred embodiment, if live cells arepresent in the product, the product is stored at a cool temperature suchas, for example, less than 20° C., 15° C., 10° C., or 5° C. On the otherhand, a biosurfactant composition can typically be stored at ambienttemperatures.

In one embodiment, the subject invention provides yeast fermentationproducts that can be used to digest, or enhance the degradation of,polymers in fracking wells. The yeast fermentation product can beobtained via cultivation of a biosurfactant-, solvent- and/orenzyme-producing yeast, such as, for example, Wickerhamomyces anomalus(Pichia anomala). The fermentation broth after 7 days of cultivation at25-30° C. can contain the yeast cell suspension and, for example, 4 g/Lor more of biosurfactant.

The yeast fermentation product can also be obtained via cultivation of abiosurfactant-, solvent- and/or enzyme-producing yeast, such as, forexample, Starmerella bombicola. The fermentation broth after 5 days ofcultivation at 25° C. can contain the yeast cell suspension and, forexample, 100 g/L or more of biosurfactant.

In one embodiment, the composition according to the subject invention isobtained through cultivation processes ranging from small to largescale. The cultivation process can be, for example, submergedcultivation, solid state fermentation (SSF), and/or a combinationthereof.

The microorganisms in the microbe-based composition may be in an activeor inactive form. The microorganisms can be in vegetative form, sporeform or any other form of microbial propagule, or a combination thereof.The microbe-based products may be used without further stabilization,preservation, and storage. Advantageously, direct usage of thesemicrobe-based products preserves a high viability of the microorganisms,reduces the possibility of contamination from foreign agents andundesirable microorganisms, and maintains the activity of theby-products of microbial growth.

Local Production of Microbe-Based Products

In preferred embodiments of the subject invention, a microbe growthfacility produces fresh, high-density microorganisms and/or microbialgrowth by-products of interest on a desired scale. The microbe growthfacility may be located at or near the site of application. The facilityproduces high-density microbe-based compositions in batch,quasi-continuous, or continuous cultivation.

The distributed microbe growth facilities of the subject invention canbe located at the location where the microbe-based product will be used(e.g., a mine) or near the location of use. For example, the microbegrowth facility may be less than 300, 250, 200, 150, 100, 75, 50, 25,15, 10, 5, 3, or 1 mile from the location of use.

Because the microbe-based product is generated locally, without resortto the microorganism stabilization, preservation, storage andtransportation processes of conventional microbial production, a muchhigher density of live microbes in a vegetative or propagule state canbe generated, thereby requiring a smaller volume of the microbe-basedproduct for use in the on-site application or which allows much higherdensity microbial applications where necessary to achieve the desiredefficacy. This allows for a scaled-down bioreactor (e.g., smallerfermentation tank, smaller supplies of starter material, nutrients, pHcontrol agents, and de-foaming agents) with no reason to stabilize thecells or separate them from their culture broth, which makes the systemefficient and facilitates the transportability of the product.

Local generation of the microbe-based product also facilitates theinclusion of the growth broth in the product. The broth can containagents produced during the fermentation that are particularlywell-suited for local use.

Locally-produced high density, robust cultures of microbes are moreeffective in the field than those that have undergone vegetative cellstabilization or have sat in the supply chain for some time. Themicrobe-based products of the subject invention are particularlyadvantageous compared to traditional products wherein cells have beenseparated from metabolites and nutrients present in the fermentationgrowth media. Reduced transportation times allow for the production anddelivery of fresh batches of microbes and/or their metabolites at thetime and volume as required by local demand.

The microbe growth facilities of the subject invention produce fresh,microbe-based compositions, comprising the microbes themselves,microbial metabolites, and/or other components of the broth in which themicrobes are grown. If desired, the compositions can have a high densityof vegetative cells or a mixture of vegetative cells, reproductivespores, conidia, and/or mycelia.

Advantageously, the compositions can be tailored for use at a specifiedlocation. In one embodiment, the microbe growth facility is located on,or near, a site where the microbe-based products will be used.

Advantageously, these microbe growth facilities provide a solution tothe current problem of relying on far-flung industrial-sized producerswhose product quality suffers due to upstream processing delays, supplychain bottlenecks, improper storage, and other contingencies thatinhibit the timely delivery and application of, for example, a viable,high cell-count product and the associated broth and metabolites inwhich the cells are originally grown.

Advantageously, in preferred embodiments, the systems of the subjectinvention harness the power of naturally-occurring local microorganismsand their metabolic by-products to improve oil production. The microbegrowth facilities provide manufacturing versatility by the ability totailor the microbe-based products to improve synergies with destinationgeographies. Local microbes can be identified based on, for example,salt tolerance, and ability to grow at high temperatures.

The cultivation time for the individual vessels may be, for example,from 1 to 7 days or longer. The cultivation product can be harvested inany of a number of different ways.

Local production and delivery within, for example, 24 hours offermentation results in pure, high cell density compositions andsubstantially lower shipping costs. Given the prospects for rapidadvancement in the development of more effective and powerful microbialinoculants, consumers will benefit greatly from this ability to rapidlydeliver microbe-based products.

In one embodiment, the composition according to the subject invention isobtained through cultivation processes ranging from small (e.g., labsetting) to large (e.g., industrial setting) scales. These cultivationprocesses include, but are not limited to, submergedcultivation/fermentation, solid state fermentation (SSF), andcombinations thereof.

Advantageously, the microbe-based products can be produced in remotelocations. The microbe growth facilities may operate off the grid byutilizing, for example, solar, wind and/or hydroelectric power.

Enhanced Oil and Gas Recovery and Enhanced Polymer Degradation andRecovery

In one embodiment the subject invention provides a method of improvingoil and gas well performance, or enhancing oil and gas recovery, byenhancing the degradation of polymeric additives utilized in fracturingfluids, as proppant coating, or in frac balls.

The method can also be useful for well completion, particularly infracking operations, as well as restoring the health of oil andgas-bearing formations (i.e., rejuvenation of older fracked formations).For example, the subject compositions and methods can aid in the repairof formation damage in the areas surrounding a wellbore, and canremediate polymers (e.g., PLA and PGA) and biopolymers (e.g., guar gumand xanthan gum) that are left over from previous fracking operations.Thus, clogged channels can be opened up within formations to allow forfurther fracking opportunities.

In one embodiment the method comprises applying a composition comprisingone or more strains of microorganisms, and/or a growth by-productthereof, to an oil well undergoing hydraulic fracking treatment. Thegrowth by-product can be any microbial metabolite, such as, for example,a biosurfactant, a solvent and/or an enzyme. This method can be appliedto vertical wells as well as horizontal wells.

Preferably, the microbes of the microbe-based composition and/or theirgrowth byproducts can quickly digest polymers, such as, e.g., PLA orPGA; thus, the method can improve the ability to recover hydrocarbonresources by reducing the buildup of PLA, PGA, or other polymers and/orresins within the fractures and wellbores of fracking wells.

In one embodiment, the microorganism is a yeast, for example,Wickerhamomyces anomalus and/or Starmerella bombicola. In oneembodiment, the microorganism is a bacteria, such as, for example, aspecies of Bacillus clade bacteria. In one embodiment, a combination ofmicroorganisms is utilized in the microbe-based composition. The microbecan be live (or viable), or in spore form, at the time of application.

The microorganisms can grow in situ and produce active compounds onsite.Consequently, a high concentration of, for example, biosurfactant,solvent, and/or enzyme, and biosurfactant-producing microorganisms at atreatment site (e.g., an oil well) can be achieved easily andcontinuously.

The method can further comprise adding materials to enhance microbegrowth and/or germination during application (e.g., adding nutrients topromote microbial growth and/or germination enhancers). In oneembodiment, the nutrient sources can include, for example, nitrogen,nitrate, phosphorus, magnesium and/or carbon. In one embodiment, thegermination enhancers can include, for example, L-alanine, L-valine,L-asparagine and/or manganese in micromolar amounts.

In one embodiment, the method can further comprise addingpolymer-degrading enzymes to the site in order to enhance polymerdegradation.

The method can be performed in situ by applying the composition andoptional nutrients and/or other agents directly in an oil reservoir orin fracking fluid.

In one embodiment, the treatment can be applied down the casing of awell using standard pumping and/or coiled tubing. A pump at the surfaceof the well forces the composition fluid into the formation, and thetubing helps to isolate different fracking zones so that all zoneswithin the well can be reached. Some wells can have as many as 20 ormore different frack zones.

In one embodiment, the amount and concentration of the microbe-basedcomposition applied to the well is determined by the length of the frackzone and the depth of the well. For example, the volume of treatmentapplied can range from 300 gallons to 3,000 gallons or more.

In one embodiment, the treatment is applied after primary fracking iscompleted, for example, up to five or more years afterward. In anotherembodiment, the treatment is applied once the well starts losingproduction due to polymer build up. In another embodiment, the treatmentis applied immediately after fracking has been completed.

In one embodiment, the method can further comprise the step of applyingheat to the fracking treatment in order to further speed up the rate ofpolymer degradation.

In one embodiment, the subject invention provides methods of producing apolymer-degrading enzyme by cultivating a microbe strain of the subjectinvention under conditions appropriate for growth and enzyme production;and optionally, purifying the enzyme.

The methods of the present invention can be used to degrade a variety ofpolymers, particularly those used as additives in hydraulic fracturingfluids. Non-limiting examples of polymers include polylactic acid, orpoly(lactic acid), or polylactide (PLA), other polyesters, guar-basedadditives, starches, polybutylene adipate terephthalate (PBAT),polyhydroxyalkanoates (PHAs), polyacrylamide (PAM), polybytlenesuccinate (PBS), polycaprolactone (PCL), polyglycolic acid (PGA),polyhydroxybutyrates (PHBs) and/or blends of these materials. Theproperties, including degradation time under selected environments, ofsuch polymers can depend on molecular weight distribution,crystallinity, co-polymers and additives.

In preferred embodiments, the present invention can be used to degradepolylactic acid, or PLA. PLA is a biodegradable thermoplastic polyesterwith a melting point of around 150° C. It been used, for example, tomake food safe containers, molded parts, films, foams, fibers, and as amaterial for 3D printing. In the oil and gas industry, PLA is used as anadditive in fracturing treatments for increasing the productivity offracking wells. For example, PLA fibers are used to prevent proppantflowback, and PLA flakes and balls are used as friction reducers andbreakers.

In further embodiments, the present invention can be used to degradepolyglycolide, or PGA. PGA is also a biodegradable thermoplasticpolyester with a melting point of around 200° C. It has been used, forexample, to make medical implants and drug delivery carriers, as well asabsorbable sutures. In the oil and gas industry, PGA has been used as atime release agent for corrosion inhibitors, a dispersant, adecomposition inhibitor for lubricants in moving equipment, a divertingagent, or to dissolve scale and prevent corrosion, or in the form offracking balls to allow for zone fracking.

PLA and PGA can be derived from chemical synthesis or from renewableresources, for example, from fermentation of sugar or cornstarch. PLAcan also be produced from petroleum. Because of the chemical propertiesof PLA and PGA, these particular polymers can take days or even monthsto degrade using, for example, water or other natural processes alone.

Thus, the present invention is advantageous in that it providescompositions and methods for degrading, or enhancing the degradation of,polymers such as PLA or PGA that can build up in fracking wells anddecrease productivity of wells. As used herein, “enhanced degradation”refers to decreasing the time for degradation to occur.

In one embodiment, the subject invention provides methods of recovering,or bringing to the surface, polymeric substances that remain in frackingwells. For example, biosurfactants produced by methods andmicroorganisms of the present invention can reduce interfacial tensionof fluids. Thus, the fluids can then be used for uplifting polymericfracking substances, such as polyacrylamide (PAM) gel friction reducers,with greater ease and less energy expenditure. In another embodiment,the biosurfactants can be used to cleave PAM gel.

In another embodiment, the microbe-based products and compositions ofthe subject invention can be used in wells undergoing acid frackingtreatments. In acid fracturing, acids such as hydrochloric acid, formicacid, and acetic acid, are used to etch channels into the rock formationof a well. Diverters are used to create barriers in certain perforationsin the formation, thus directing acid to other desired areas.

In one embodiment, methods are provided for remediating, i.e.,degrading, acids and other diverters used in acid treatments usingmicrobe-based compositions of the subject invention. In particular, amethod of remediating benzoic acid diverters is provided, comprisingapplying the microbe-based compositions of the subject invention to awell undergoing acid fracturing.

Benzoic acid flakes or powder are soluble in toluene, xylene, alcohol,and some condensate fluids, but they dissolve very slowly in water orgas. Benzoic acid is often used as a diverter because it is soluble inthe fluids normally encountered in wells; however, if not well dispersedor mixed, it will plug perforations. When such a plug occurs, it cannotbe dissolved quickly because of decreased fluid flow. For example,benzoic acid plugs can take six months or more to return to normalproductivity after being treated with benzoic acid.

EXAMPLES

A greater understanding of the present invention and of its manyadvantages may be had from the following examples, given by way ofillustration. The following examples are illustrative of some of themethods, applications, embodiments and variants of the presentinvention. They are not to be considered as limiting the invention.Numerous changes and modifications can be made with respect to theinvention.

Example 1—Cultivation of Wickerhamomyces anomalus and Starmerellabombicola Yeast Products

Seed culture be maintained by streaking fresh liquid culture on potatodextrose agar plate and growing the seed culture at 30° C. for 3 days.Afterwards, the plates of seed culture can be stored at 4° C. for amaximum of 2 weeks.

YGSU medium was used for cultivating the yeast. For W. anomalus, theinitial pH was adjusted to 5.5. Seed culture was transferred from theagar plate to a 1 L flask with a working volume of 200 mL. The culturewas cultivated in a shaker at 30° C. with a shaking speed of 200 rpm.After 7 days, biosurfactants were observed as a brown precipitate layer,with concentration around 4 g/L.

For S. bombicola, the fermentation broth after 5 days of cultivation at25° C. can contain the yeast cell suspension and, for example, 100 g/Lor more of biosurfactant.

Example 2—Treatment of PLA Balls with Yeast Product

As shown in FIGS. 1 and 2, the yeast fermentation products can beincubated with fracking fluid containing, for example, PLA balls, for 24hours. A PLA ball after incubation with the yeast fermentation productwas completely dissolved, whereas when incubated for the same timeperiod with water alone, only 1% total dissolution occurred (requiringapproximately one month to dissolve completely).

The invention claimed is:
 1. A method of recovering a polymer used inhydraulic fracking fluids from a fracking well, wherein the polymer ispolyacrylamide (PAM) gel, wherein the method comprises applying acomposition comprising a fermentation broth in which one or moremicroorganisms were cultivated, said fermentation broth comprising theone or more microorganisms and/or a growth by-product thereof, andoptionally, one or more nutrients and/or germination enhancers, to afluid, injecting the fluid into the well, and uplifting the PAM gel fromthe well using the fluid, wherein the one or more microorganisms areselected from Starmerella bombicola and Wickerhamomyces anomalus.
 2. Themethod of claim 1, wherein prior to uplifting, the PAM gel is cleaved bythe composition.
 3. The method of claim 1, wherein the growth by-productis a glycolipid biosurfactant.